1. Field of the Invention
The present invention relates to a method for modification of alginates and other uronic acid substances to obtain changes in the functional properties, in particular with respect to the ability of forming gels with inorganic or organic polyvalentions.
2. Prior Art
Alginates are manufactured from brown sea-weed and are utilized in several applications where their polyelectrolytic nature forms the basis for e.g. gelation, thickening as well as water- and ion-binding.
Chemically speaking, alginates constitute a group of linear, binary copolymers built up of salts of .beta.-D-mannuronic acid (M) and its C-5 epimer, .alpha.-L-guluronic acid (G). The M and G units are found in three types of sequences; G-rich sequences called G-blocks, M-rich sequences called M-blocks, and alternating sequences found in MG-blocks, symbolized MGMG. The fractional content of these monomer units as well as their sequencial distribution varies with the algal source. The ion binding and gelforming properties depend on the monomer fractions, but in particular on the distribution of G-units along the chain. A high content of G-blocks leads to the technically important gel-forming properties.